Process for producing foam fabrics



June 25, 1968 R. G. FARRISH PROCESS FOR PRODUCING FOAM FABRICS FiledJan. 25, 1966 lillun i-ET INVENTOR ROBERT GUY PARRISH ATTORNEY UnitedStates Patent 3,389,446 PROCESS FOR PRODUCING FOAM FABRICS Robert GuyParrish, Sharpley, Wilmington, Del., assignor to E. I. du Pont deNemours and Company, Wilmington, Del., a corporation of Delaware FiledJan. 25, 1966, Ser. No. 522,935

' 5 Claims. (Cl. 28-76) ABSTRACT OF THE DISCLOSURE Foam fabrics areproduced by a process which includes the steps of flash-extruding asolution of an organic polymer to form closed cell, gas-inflated foamfilaments, collapsing the filaments by reducing the quantity of gaswithin the cells, forming the filaments While collapsed into a fabric,then re-inflating the filaments by introducing gas into the cells.

This invention relates to fabrics comprised of foamed polymericfilaments. More particularly, it relates to an improved method forforming these fabrics, by weaving, knitting, or needling, usingclosed-cell foam-filaments with collapsed cells.

Foamed materials, especially foils or sheets of resilient polyurethanefoam, have become very popular in fabric applications. They provide bulkwithout extra weight, and their thermal insulation properties areexcellent for cold weather apparel. In some applications, such ascar-pet backing, foams also provide outstanding cushioning properties.These polyurethane foam foils have, however, severe disadvanta-ges. Theyare weak and easily torn, and they are visually unattractive especiallybecause they tend to yellow severely on exposure to the atmosphere.Consequently, it has been necessary to laminate them on one or bothfaces to customary fabrics. Besides being expensive, lamination leads toproblems from delamination, as is well understood.

An obvious means for imparting the advantages of foam to fabrics whileavoiding lamination/delamination problems is to manufacture the fabricfrom foam-filaments. Many known resilient foams in filament form are,however, too weak to Withstand the stresses of weaving, knitting, orneedling. Moreover, at the desirably low foam densities of about 0.05gm./cc. or less, the length of filament that can be wrapped on a yarnpackage is so limited that fabric formation can proceed only for a veryshort interval before filament ends are encountered.

In US. Patent No. 3,100,926 is described a method a for providingfabrics of foamed filaments whereby weaving is done with solidthermoplastic filaments containing a thermally decomposable blowingagent. Heating of the woven fabric to a sufiiciently high temperaturecauses the filaments to foam and also to fuse at all the filamentcross-over points. While this method avoids some of the above problems,it cannot provide fabrics with customary fabric drape because of theunavoidable fusion at cross-over points.

The disadvantages of heretofore known processes for constructing fabricscomprising foams are overcome by the process of this invention whichcomprises the steps of (l) forming a fabric using collapsedmicrocellular filaments and (2) post-inflating the fabric to providetightness-of-weave, cover, drape, bulk, and resilience.

A microcellular filament is generally composed of polyhedral-shaped,closed, uniform-sized foam cells of which the maximum transverse celldimensions should be less than about 1000 microns. Each cell is a voidor gas-filled space completely enclosed by cell walls which arefilm-like elements of thermoplastic synthetic-organic polymer less thanabout 2 microns thick and substantial- 3,389,446 Patented June 25, 19681y uniform in thickness over the whole area of each cell Wall.Substantially all of the polymer is in these cell walls rather thanbeing concentrated at the cell wall intersections. A minor proportion ofcell walls may be ruptured to produce tunnel-like cells generallyoriented parallel to the filament axis, but extrusion conditions arepreferably chosen to minimize the formation of tunnel-like cells.

Microcellular filaments can be formed directly by extrusion of foamablesolutions through extrusion orifices. A point of maximum cell expansionis reached shortly after exit from the orifice, .at which point eachcell wall solidifies so that its area is fixed. Methods are known bywhich gases can be introduced to or withdrawn from the foam cellswithout harming their integrity or low gas permeability. Introduction ofgases expands the cells, but only to the maximum sizes reachedimmediately following extrusion, after which more gas introductionincreases pressure within the cells to supenatmospheric values withsubstantially no increase in cell volume. On continuous withdrawal ofgases, however, a pressure less than atmospheric is created within thecells; and then ambient external gas pressure causes each cell todecrease in volume by wrinkling and folding of its cell walls, whichremain constant in area. A microcellular filament is said to be collapedif its cross-sectional area (i.e., its volume) is less than 50%, andpreferably less than 25%, of that characteristic of the fully inflatedstate.

Microcellular filaments in the fully inflated state have densities inthe range from about 0.005 gm./cc. up to about 0.05 gm./cc. On collapseof these microcellular filaments, density naturally increases; and fullycollapsed filaments can have densities which are as high as of thedensity of the unfoamed solid polymer of which they are comprised.Typical densities for collapsed microcellular filaments are in the rangefrom 0.1 to 0.3 gm./cc. This high degree of collapsibility results notonly from the flexibility of the ultrathin cell walls but also from thehigh ratio of maximum transverse dimension to wall thickness for eachcell. This ratio for microcellular foams is ordinarily in the range fromabout 30 to 3,000.

FIGURE 1 is a perspective view of a portion of a woven fabric comprisedof collapsed microcellular filaments.

FIGURE 2 represents the fabric of FIGURE 1 after its microcellularfilaments have been post-inflated.

Weaving, knitting, or needling with collapsed microcellular filaments isaccomplished with the same equipment and techniques well-known forcustomary dense, non-foamed filaments or yarns whether they be ofsynthetic or natural origin. A loosely woven fabric 10 as in FIGURE 1 isformed to have both warp and weft of collapsed microcellular filaments13. On introduction of gases by a post-inflation technique, describedhereinafter, the collapsed microcellular filaments 13 are converted tothe fully inflated filaments 15 of FIGURE 2.

Fabric construction is in no way limited to that illustrated by FIGURES1 and 2. Thus, both warp and weft can be only of microcellularfilaments, or either can be comprised of both microcellular filaments 13and dense unfoamed filaments or yarns in any proportion. Likewise,knitting or needling techniques can be used to form fabrics comprisingcollapsed microcellular filaments. Fabric formation is followed bypost-inflation of the collapsed filaments. A loosely woven scrim 10, forexample, is thereby converted to a tight, resilient and opaque fabric 20which can become much more tightly woven than if fully inflatedfilaments were employed during weaving.

Loosely woven scrims containing collapsed microcellular filaments 13 areparticularly useful in another aspect of this invention which is themanufacture of a novel tufted structure. Tufts are easily inserted intothe large openings of scrim which is then post-inflated to firmly lockthe tufts into the fabric. The structure then serves as a tufted carpetwith both bulk and resilient cushioning provided by the inflatedmicrocellular filaments. The carpeting so obtained is an integralstructure devoid of adhesive bonding, stitching, or lamination; and thefoam in the structure has high frictional properties which provideanti-skid performance.

When dense yarns and microcellular filaments are to be combined in afabric construction, it is occasionally preferred to use sheath-corefilaments in which the core is a dense yarn and the sheath is collapsedmicrocellular foam. Such sheath-core yarns are particularly advantageouseither when the microcellular filament without a core is too Weak towithstand the stresses of fabric formation, or when it is aestheticallyor chemically desirable to completely cover the dense yarn.

For some fabrics, the need for tightness-of-weave, cover, and opacityrequires the use of so much customary dense yarns that the tensile andtear properties of the fabrics far exceed those required for the fabricend-use. Certain synthetic textile yarns with otherwise superiorproperties are frequently excluded from such end-use applicationsbecause of their cost. When such fabrics are woven from both collapsedmicrocellular filaments I3 and dense unfoamed yarns, only enough denseyarn is used to provide the desired fabric strength properties.Post-inflation of the microcellular filaments 13 separately provides therequired cover and tightness of weave while at the same timeaccomplishing a reduction in both area weight and cost of the finishedfabric. Not only can the use of microcellular filaments result in moretightly woven fabrics than can otherwise be obtained, but also iteliminates the added expense of weaving tightly and decreases the numberof ends and picks required. As is obvious to one skilled in the art,separate provision of strength and cover is extremely valuable to fabricdesigners.

A characteristic of collapsed microcellular filaments which renders themsuperior to inflated filaments for weaving or knitting is theirsignificantly higher tensile strength. Thus they are better able toWithstand weaving stresses. Their higher strength presumably resultsfrom the lack of pre-stress present in inflated foam cells and also fromthe fact that cell collapse brings more cell Walls into parallelism withthe filament axis.

The surfaces of callpsed microcellular filaments have much lessfrictional resistance to sliding than do the surfaces of inflated foamfilaments, which greatly facilitates weaving and knitting. When fullyinflated, a foam filament presents a large surface which, since it isdrawn taut, is completely exposed for frictional contact. Althoughusually detrimental to Weaving or knitting, these frictional forces arefrequently desirable in finished fabrics. The collapsed microcellularfilament, by virtue of its decreased diameter, has less surface; thesurface is denser and smoother; and less of the surface is con'tactablebecause of the wrinkled cross-sectional margin formed during collapse.

Finally, filament length remains substantially constant during collapseand inflation. This is in direct contrast to dense filaments containingsolid blowing agents. When the latter are foamed by thermal treatmentafter fabric formation, they enlarge in all dimensions so that foamingcannot produce as tight a fabric. Collapsed microcellular filaments havealready been inflated and have collapsed under external atmosphericforces directed normal to the filament surface. Thus, the cell WallsWrinkle and fold only to form a smaller diameter with substantially nochange in length. On post-inflation, the cell Walls unfold to provide alarger diameter, again with substantially no change in filament length.

Microcellular filaments useful in this invention have fully inflateddiameters generally in the range from about 0.01 inch (0.025 em.) up toabout 0.25 inch (0.64 cm.), but inflated filaments up to 1.0 inch (2.5cm.) or more can readily be provided. Collapsed microcellular filamentsnormally have effective diameters of from about 0.1 to 0.5 times thecorresponding fully inflated diameter. Since they frequently flatten toa ribbon-like shape during collapse, effective diameter becomes maximumfilament width.

The preferred microcellular filaments for use according to thisinvention are ultramicrocellular as disclosed in Blades et al. U.S.Patent 3,227,664, filed Jan. 31, 1962. By virtue of their crystallinityand of their high level of unique uniplanar crystallite orientation,ultramicrocellular filaments are very strong. In addition, bothuniplanar orientation and uniform texture (as defined therein) rendertheir cell Walls particularly resistant to gas permeation.-

Foamed filaments useful in the process of this invention are comprisedof thermoplastic polymers, e.g., polyhydrocarbons such as polyethylene,polypropylene, or polystyrene; polyethers such as polyformaldehyde;vinyl polymers such as polyvinylidene fluoride or polyvinyl chloride;polyamides both aliphatic and aromatic, such as polyhexamethyleneadipamide and po'lynietaphenylene isophthalamide; polyurethanes, bothaliphatic and "aromatic, such as the polymer from ethylenebischloroformate and ethylene diamine; polyesters such aspolyhydroxypivalic acid and polyethylene 'terephthalate; copolymers suchas polyethylene terephthalate-isophthalate; polynitriles such aspolyacrylonitrile and polyvinylidene cyanide; poly-acrylates such aspolymethyl met-hacrylate; and equivalents. The polymers must be of atleast film-forming molecular Weight.

One of the features of the preferred ultramicrocellular material is itshigh degree of molecular orientation in the cell walls, whichcontributes to its unique strength. Therefore, a preferred class ofpolymers from which to make foam-filaments for use in this process isone including polymers which respond to orienting operations by becomingsubstantially tougher and stronger. This class is Well-known to oneskilled in the art and includes, for example, linear polyethylene,stereo-regular polypropylene, 6-nylon, and polyethylene terephthalate. Afeature of any inflated microcellular material is its pneumaticityresulting directly from its unique structure, which may be regarded asmultitudinous tiny bubbles of gas enclosed in thin polymer skins.Retention of this gas, and hence of the pneumaticity of the structure,depends on a low rate of gas permeation through the cell walls. Afurther preferred class of polymers for preparing microcellular materialcontains those polymers for which permeability coeflicients for mostgases are low, s-uchas polyethylene terephthalate and polyvinylchloride.

In the preparation of microcellular materials, various polymer additivessuch as dyes, pigments, antioxidants, delusterants, antistatic agents,reinforcing particles, adhesion promoters, ion exchange materials,ultraviolet stabilizers and the like may be incorporated provided theparticle sizes are not so large as to interfere with the extrusionoperation.

If, in the extrusion of microcellular filaments, the volatile blowingagent employed is one which permeates the polymeric cell walls muchfaster than air, the blowing agent Will diffuse out from the foam beforeit can be replaced with air, and the filament will collapse. This is thepreferred means for providing collapsed filaments according to thisinvention. Further preferred are those blowing agents which, cooled bytheir own expansion after extrusion, liquefy to cause very rapidfilament collapse. Methylene chloride, for example, is very volatile,permeates cell walls faster than air, and liquefies at room temperatureso that its use as a blowing agent results in suitable collapsed butreinflatable filaments without further treatment.

Fully or partially inflated microcellular filaments can be collapsed byimmersion in a bath containing a readily volatilized liquid which weaklyplasticizes the cell walls and temporarily increases the rate ofpermeation without permanently affecting crystallinity or molecularorientation of polymer in the cell walls. In the bath, the inflating gasescapes by rapid permeation; and the filament collapses in diameter. Theweakly plasticizing liquid is then removed by vaporization to form astrong, collapsed but reinfiatable microcellular filament. Methylenechloride and fluorotrichloromethane are examples of frequently effectiveweak plasticizers for this use.

Post-inflation of microcellular filaments is readily accomplished byimmersing them in a bath containing both a volatile weakly plasticizingcomponent and a component which is normally gaseous at ambienttemperature and which permeates the cell walls more slowly than air. Onremoval from the bath and on rapid vaporization of the weaklyplasticizing component, the slowly permeating component is trappedwithin the cells providing an osmotic gradient for the inward permeationof air and reliable post-inflation. Equilibration with air is frequentlyspeeded by brief warming of the filaments to temperatures usually lessthan or about 125 C. When the slower permeating component hasessentially a zero permeation coefficient as compared to that for air,it is termed an impermeant inflatant. Presence of an impermeantinfiatant within the foam cells results not only in full inflation ofthe filament but also in spontaneous osmotic reinflation if compressiveloading has caused the outward permeation of some of the contained air.

The rate of permeation for an inflatant through a given polymerincreases as its diffusivity and solubility increase. Accordingly,candidates for impermeant infiatants should have as large a molecularsize as is consistent with a sufficiently great vapor pressure atambient temperatures, which is preferably 50 mm. of mercury or greater,and they should have substantially no solvent power for the polymer. Apreferred class of impermeant infiatants is exemplified by compoundswhose molecules have chemical bonds different from those in theconfining polymer, a low dipole moment, and a very small atomicpolarizability.

Suitable impermeant inflatants are selected from the group consisting ofsulfur hexafluoride and saturated aliphatic and cycloaliphatic compoundshaving at least one fluorine-to-carbon covalent bond and wherein thenumber of fluorine atoms exceeds the number of carbon atoms. Preferablythe saturated aliphatic and cycloaliphatic inflatants are, respectively,perhaloalkanes and perhalocycloalkanes in which at least 50% of thehalogen atoms are fluorine. Although these inflatants may containether-oxygen linkages, they are preferably free from nitrogen atoms,carbon-to-carbon double bonds, and reactive functional groups. Specificexamples of impermeant inflatants include sulfur hexafluoride,perfluorocycl obutane. symdichlorotetrafluoroetha-ne, perfluoro 1,3dimethylcyclobutane, perfluorodimethylcyclobutane mixtures,l,l,2-trichloro-l,2,2- trifluoroethane, CF CF CF OCFHCFchlorotrifiuoromethane, and dichlorodifluoromethane. Mixtures of two ormore impermeant infiatants can often be used to advantage.

It will be understood that impermeant inflatants must be inert; i.e.,they must be chemically stable under conditions of use for fabricscontaining inflated microcellular filaments.

A broad range of fabric types can be obtained according to thisinvention. In addition to the relatively simple net-like fabricsdescribed, much more complex fabrics are readily woven. By properprogramming of the weaving operation and/or by employing two or morewarps simultaneously, it is possible to produce layered wovens in whichdecorative customary fabrics are formed on either or both faces of alayer of microcellular filaments. Or collapsed microcellular filamentscan be used in multiple layers which, after post inflation, result in athick, bulky, tightly woven fabric. Customary knitting machines cancreate a 'variety of knit goods containing microcellular filaments.Loops of microcellular filaments extending out from a face of a net-likefabric can be formed by needling, or net-like fabrics of microcellularfilaments can be needled or tufted with other yarns. In every case, thecollapsed microcellular filaments incorporated in the fabric duringformation are subsequently post-inflated to yield the desired finalproduct.

Fabrics produced in accordance with this invention are useful, forexample, as upholstery materials, as substrates for vinyl-calenderedupholstery materials, as cushioning and insulating clothing fabrics, ascushioning mats or carpets and for decorative wall hangings.

Because many variations of the process of this invention are obvious toone skilled in the art, the following examples are intended toillustrate but not to limit the invention, except as provided in theappended claims.

Example I This example is a plain-weave fabric comprising onlymicrocellular filaments. The filaments were obtained by extruding apolymer solution through a circular orifice of 0.020 inch (0.51 mm.)diameter into the ambient atmosphere. The homogeneous polymer solutionwas formed in a three-liter cylindrical pressure vessel containing 1,000gms. of Profax stereo-regular polypropylene (Hercules Powder Co.), 750cc. of methylene chloride, and 250 gms. of trichlorofluoromethane.Dispersed throughout these components was 5 gms. of finely dividedSantocel54 silica aerogel (Godfrey L. Cabot, Inc.). While the pressurevessel was rotated end over end, it was heated to C. and kept at thattemperature for 16 hours under autogenous pressure. At the end of thattime, 320 p.s.i.g. (22.5 kg./ cm. gauge) of nitrogen pressure wasapplied. The extruded filament collapsed within seconds after extrusionto about 0.060 in. (1.5 mm.) in diameter at 535 denier.

The plain-weave fabric construction used 14 ends and 8 picks per inch(about 5.5 ends and 3.15 picks per cm.) of these collapsedultramicrocellular filaments. After immersing the fabric in a roughly50:50 (vol/vol.) mixture of methylene chloride and1,1,2-trichloro-1,2,2-trifluoroethane, it was removed and dried in warmair. While drying, the filaments post-inflated to create a fabric sotight in weave as to have been impossible to obtain by weaving a fullyinflated microcellular filament.

Example II This example illustrates the use of a filament With a densefiber core and a collapsed microcellular sheath to form a Bedford cordtype of fabric. The core was approximately 260 denier 66-nylon yarnsheathed in approximately 400 denier ultramicrocellular polypropylene.This sheath-core filament replaced the heavy cotton-warp cords in anotherwise typical Bedford cord weave. The woven fabric exhibited only aslight cording effect in the warp direction; but after post-inflation asin Example I, fabric thickness increased from about 0.030 in. (0.76 mm.)to about 0.055 in. (1.40 mm.) and the cording effect became pronounced.At the same time, a considerably lighter fabric was obtained byreplacing the customarily heavy cotton cords with this light sheath-corefilament.

Even lighter, but otherwise substantially identical, Bedford cordsresulted when unsupported, collapsed, ultramicrocellular, polyethyleneterephthalate filaments were used in place of the above sheath-corefilaments.

Example III This example illustrates the use of this invention toprovide a cushioning bulky automotive upholstery fabric. Two separatebatches of microcellular filament were used. Both were prepared bycharging a l-liter cylindrical pressure vessel with 440 gms. ofhigh-molecular-weight polyethylene terephthalate, previously dried at206 C., and 300 ml. of dry methylene chloride, pressurizing the vesselwith nitrogen gas, heating the contents to 220 C., holding them at thattemperature for 30 minutes, and then extruding through a circularspinneret. In one case the nitrogen pressune was 850 p.s.i.g. (59.8kg./cm. gauge), the spinncret was 0.020 in. (0.508 mm.) in diameter and0.040 in. (1.16 mm.) in length, and the ultramicrocellular filamentformed was of 760 denier with a fully inflated diameter of 0.104 in.(2.6 mm.). In the other case the extrusion pressure was 950 p.s.i.g.(66.9 kg./cm. gauge) and the spinneret was 0.030 in. (0.76 mm.) indiameter and 0.060 in. (1.52 mm.) in length. This fully inflatedfilament had a diameter of 0.149 in. (3.8 mm). Within seconds afterextrusion, however, both of these products collapsed into narrowribbon-like filaments with widths of about half the diameters specifiedabove.

Fabric construction used a double warp, the first of which employed 3types of yarns: 140/68/.5 Z type 180 nylon, 200/20/.75 Z nylon and70//.5 Z black nylon. The second warp was completely of the abovecollapsed ultramicrocellular filaments. The ratio of warp ends for thesefour types of filaments, in the order given, was 104:32z24t3. The fillwas 12/2 spun rayon yarn plus various decorative yarns includingmetallic luster yarns. Programming of the filling picks was such thatthe first warp was converted to a decorative cover fabric whilesimultaneously the warp of collapsed filaments was lightly stitched toits lower surface. The woven fabric was then dyed to a medium blue shadeby a process appropriate to the dense conventional fibers used, whichprocess had no effect on the collapsed ultramicrocellular filaments.Then the fabric was immersed in a boiling 50:50 by volume mixture ofmethylene chloride and 1,1,2-trichloro-1,2,2- trifiuoroethane. Removedfrom this bath, the fabric was put through a pin tenter at approximately200 F. (93 C.) which treatment resulted in a greater than 2 increase indiameter of the ultramicrocellular filaments. The inflated filamentsprovided a substantially continuous, close-packed, backing layer. Fabricthickness before inflation was about 0.065 in. (1.65 mm.) increasing toabout 0.120 in. (3.05 mm.) thereafter. The foam-layer contributed body,fullness, and excellent cushioning to the fabric. The Weave designcreated a warp-wise wide rib effect which, without the cushioning foambacking, would have readily crushed in use.

Example IV A novel, thick, woven, cushioning pad, obtainable only by thepractice of this invention, is illustrated by this example. The productsof four separate extrusions were used in constructing this fabric, butall four were as nearly identical as possible. As in Example III, 440gms. highmolecular-weight polyethylene terephthalate and 300 ml. ofmethylene chloride were charged to the pressure vessel. The contentswere heated to 220 C., held there for 15 minutes, and extruded underapproximately 900 p.s.i.g. (63.3 kg./cm. gauge) of nitrogen pressurethrough a spinneret of 0.03 in. (0.76 mm.) diameter and 0.060 in. (1.52mm.) length. These four products had deniers in the range from 2,000 to2,200, and inflated diameters in the range from 0.165 to 0.172 in. (4.2to 4.4 mm.). All these filament-s collapsed subsequent to extrusion intoflattened filaments as described in Example III.

Only these collapsed ultramicrocellular filaments were woven into afabric which was a five-layer Dobby-weave interwoven constructionemploying straight draw on twelve hardnesses. The weave diagram is notsusceptible to ready verbal description but is obvious to one skilled inthe weaving art. The off-loom, woven structure was about 0.20 in. (5.1mm.) thick. After postinflation substantially as described in ExampleIII, thickness increased to about 0.625 in. (15.9 mm.). The inflatedfilaments in this thick mat were so tightly interlocked that anapproximately 3 x 3 in. (7.6 x 7.6 cm.) piece could be cut from itscenter with no disturbance of the weave. A skilled weaver on seeing thisinflated fabric would not hesitate to state that such a structure couldnot possibly have been woven.

Example V In this example a woven structure is described in which twocustomary fabric facing layers are held apart by infiatedultramicrocellular trusses to create an insulating air space. Theultramicrocellular filaments were prepared substantially as described inExample III except that the solution was held only 20 minutes at 210 C.,the extrusion orifice was .025 x .025 in. (0.63 x 0.63 mm.), and theextrusion pressure was 675 p.s.i.g. (47.5 kg./cm. gauge). The collapsedfilaments obtained were of about 1060 denier at a density ofapproximately 0.1 gm./cc. The post-inflated diameter of these filamentswas 0.115 in. (2.9 mm.).

Two warp beams were employed. The first warp was composed of Orlonacrylic fiber yarns (E. I. du Pont de Nemours & Co., Inc.). The secondwarp was of the loosely spaced collapsed ultramicrocellular filamentsdescribed. The first warp was split by the loom so as to effectivelyprovide two warps simultaneously woven into an upper decorative fabricand a lower, more open, netlike fabric. The upper fabric could, ifdesired, be napped to produce a soft flutfy surface characteristic ofblankets. The second microcellular warp was arranged to moveincrementally at an overall greater rate than the first warp with thefoam-filaments between the forming upper and lower fabric layers.Programming of the filling yarns was such that each collapsedultramicrocellular filament was alternately stitched first to one andthen to the other of the inner fabric faces, thus forming U-shapedtrusses of the ultramicrocellular filaments. The fabric as woven wasabout 0.24 in. (6.1 mm.) thick, but the collapsed filaments were ofinsufficient rigidity to resist extensive compressive distortion. Afterpost-inflation as described in Example III, however, thickness increasedto about 0.68 in. (17.3 mm.) with the air space stabilized so that thecushioning infiated filaments recovered the initial separation aftercompression. Again, practice of this invention is the only conceivableway to obtain this blanket fabric.

Example VI The open, woven, net-like fabric of this example served as atufting substrate for a carpet. The collapsed, ultramicrocellular,polyethylene terephthalate filaments used were substantially asdescribed in Example V having a diameter in the fully inflated state of0.14 in. (3.6 mm.) and a denier of from 1200 to 1500. Weaving wascarried out on a warp having 4 ends per inch (about 1.58 ends per cm.)of the collapsed ultramicrocellular filaments, each end plied with a 200denier, 20/3/4 Z, type 860 (Du Pont) nylon yarn. The fill yarns wereinserted at 3.2 picks per inch (about 1.26 picks per cm.), each being a12/2 cc. 7/30 rayon/nylon blended yarn plied in alternate picks with anultramicrocellular filament. Because this woven fabric was so looselywoven, it was necessary to apply a sizing solution to it during weavingto prevent its disintegration on later handling. The fabric was thensupported in such a way that it was spaced above a fine screen so that,when sprayed by a water jet carrying type 501 nylon continuous filament(E. I. du Pont de Nemours & Co., Inc.), the continuous nylon filamentpassed through the openings in the fabric and onto the screen; and sincethe water jet traversed the fabric, the continuous filament looped overthe yarn elements of the fabric to create tufts. As tufted, this fabricwas not durably stable but was handleable without disintegration. It waspost-inflated substantially 'as described in Example III causing theultramicrocellular filaments to expand greatly in size and to lock thetufts into place. The tufts were uniformly distributed over the fabricat an area weight of about 10 oz./yd. (340 gm./m. The post-inflatedstructure was about 0.5 in. (about 1.27 cm.) thick, and the tuftsextended about 0.375 in. (about 0.95 cm.) above the fabric backing. Notonly did the post-inflation lock the tufts into place but at the sametime it transformed the ultramicrocellular filaments into a cushioningbase structure for the tufted carpet.

Example VII This example is a variation of the invention involvingconventional needling of collapsed microcellular filaments to aconventional burlap carpet backing to form a looppile cushioning carpet.The microcellular filaments in this example were substantially the sameas those described in Example V. The collapsed filaments wereribbon-like at a width of about 0.040 in. (1.02 mm.). A conventionalneedle-tufting apparatus was used; and, to prevent breakage of thefilaments in the eyes of the tufting needles, the filaments wereprelubricated with Clearco Knitting Oil (Clearco Products Co.).

Before post-inflation, the filaments were shaggy looking and so openthat the burlap backing was clearly visible over the whole face of thefabric. After post-inflation substantially as described in Example III,the filaments were so expanded as to make their loops close-packed,completely obscuring the burlap backing from view. The inflatedfilaments were about 0.110 inch (2.8 mm.) in diameter and protrudedabout 0.325 inch (8.25 mm.) above the burlap backing which, itself,contributed about 0.045 inch (1.14 mm.) to the total thickness.

Example VIII A Woven vinyl-substrate fabric for cushioning, bulky,furniture upholstery was prepared. The collapsed ultrarnicrocellularpolyethylene terephthalate filaments, prepared substantially asdescribed in Examples III-VI, were of about 100 denier at a density ofabout 0.30 gm./ cc. The loom was set up with two warp beams, one of theabove ultramicrocellular filaments and the other of 220/50 type 51Dacron polyester yarn (E. I. du Pont de Nemours & Co., Inc.). The loomwas a conventional power pickand-pick loom, alternating theultramicrocellular filaments and the dense yarns in an end-and-end,pick-and-pick, 2 x 2 basket weave with 40 ends and picks per inch (about15.7 ends and picks per cm.). Ruxite RK-2 finish (Laurel Soap Mfg. Co.)was sprayed ontothe warp during weaving and brushed onto the quillsprior to weaving. The fabric formed was scoured on a jig for one hour at110 F. (43.3 C.) and then dried to the wet width in air at 200 C.

After immersion for 50 minutes in a refluxing 50:50 by volume mixture ofmethylene chloride and 1,1,2-trichloro-1,2,2-trifluoroethane, the fabricwas dried on a pin tenter for minutes at 100 C. The microcellularfilaments more than doubled in diameter to yield an expanded, tightfabric 0.033 inch (0.84 mm.) thick with about 44 x 48 ends and picks perinch (about 17.3 x 18.9 ends and picks per cm.). Table I comparespertinent properties of this fabric with commercial vinyl substratefabrics. Grab tensile, elongation, and ravelled strip tests areaccording to A.S.T.M. Test Method D 168264, and tongue tear according toA.S.T.M. D 2262-64T. Where results are given in the A/ B form, A is forthe warp direction and B for the fill direction.

From Table I it is seen that the fabric of this invention is equivalentto standard vinyl substrates at considerably reduced fabric weight.

This, and other similar substrates, were readily vinylcalender-coated oncommercial equipment to provide attractive, high-bulk, cushioning,upholstery fabrics.

Example IX Collapsed, ultramicrocellular, polyethylene terephthalatefilaments as described in Example VIII were knitted coaxially with a 260denier nylon yarn into a plain jersey trioot knit. A flat-bed Dubyknitting machine was used. The ultramicrocellular filament was Wet downwith Clearco knitting oil (Clearco Products Co.), pulled from its coneunder light tension, and combined with the nylon yarn just prior toknitting. Knitting proceeded smoothly, and knits of 1015 courses perinch (3.9 to 5.9 courses per cm.) were prepared.

,These knits were scoured for 30 minutes in a home washing machinecontaining a solution of Tide detergent (Procter and Gamble) in water atISO-200 F. (82.2 to 93.3 C.). They were tumble-dried in a home laundrydrier. Post-inflation was by immersion in the bath of Example VIII for10 minutes followed by drying for 15 minutes on a tenter at C. Thefoam-filaments more than doubled in diameter to provide an attractive,bulky, pneumatic, knit fabric.

Example X The collapsed ultramicrocellular polyethylene terephthalatefilament of Example VIII as plied with one end of 100-34-0-56 Dacronpolyester yarn (E. I. du Pont de Nemours & Co., Inc.) using Dow-CorningEmulsion #36. Knitting was done on a 7-cut Duby flat-bed knittingmachine without further lubricant and with only normal tensioningdevices. Scouring, drying, and post-inflation were as described inExample IX except that Procter and Gambles Dash detergent wassubstituted for Tide." A full-cardigan knit with 12 courses and 7 walesper inch (about 4.7 courses and 2.8 wales per cm.) was prepared.

TABLE II.PROPERTIES OF THE FULL CARDIGAN KNIT Thickness 0.038 inch (0.97mm).

Area weight 1.5 oz./yd. (511 gm./m. Grab tensile 25.5/22.2 lbs.('ll.6/10.1 kg.). Elongation 133/124 percent.

Tongue tear 4.0/5.2 lbs. (1.8/2.4 kg.).

Where values above are given in the A/B form, A is machine direction andB the cross direction. The postinflated knit was attractive, bulky, andtight while being very light.

In the same fashion and with the same materials a plain jersey knit wasformed having 14 courses and 10 wales per inch (about 5.5 courses and3.9 wales per cm.).

Both of these fabrics were vinyl-calendercoated on commercial equipmentto form bulky, conformable upholstery fabrics.

TABLE I.COMPARISON OF VINYL SUBSTRATE FABRICS This example Cotton KnitCotton Cotton Osnaburgh Broken Twill Area Weight:

Oz. yd. 2.1 3.8 4.7 8.6

GrnL/m. (71) (129) (159) (292) Grab Tensile:

Kg (421/384) (ran/15.9) (201/2813) (55.7/65.1) Elongation (percent).23.3/223 50.7/1341] 9.7/13.7 PLO/16.7 Ravelled Strip:

Kg (28.8/302) (10.1/7.4) (23.6/25 .2) (424/400) Tongue Tear:

1 1 Example XI A moldable fabric backed with a layer of inflatedultramicrocellular filaments is illustrated by this example. Collapsedultramicrocellular filaments were prepared by extrusion of a foamablecomposition into the ambient atmosphere through a cylindrical orifice0.030 inch (0.76 mm.) in diameter and length. A l-liter cylindricalpressure vessel was charged with 400 gm. of high-molecularweightpolyethylene terephthalate pellets and 250 cc. (at 25 C.) of methylenechloride. The sealed pressure vessel was rotated end-over-end in a hotair oven until temperature of the contents reached 225 C. The vessel wasthen stopped with its spinning-orifice end directed downward, and 850p.s.i.g. (59.8 kg./cm. gage) of pressure from a nitrogen ballast tankwas applied through a valve near the top of the vessel. The extrudedfilament was collected as a fine, collapsed, and flattened ribbon which,after post-inflation as previously described, returned to a roundcross-section with a diameter of about 0.125 inch (0.318 cm.). Averagetransverse dimension for the fully inflated foam cells was about 20microns. Density of the inflated filament was about 1.0 lb./ft. (0.016gm./cc.).

A fabric was woven using two warps, one of which was composed of theabove collapsed, approximately 0.0625 inch (0.159 cm.) wide,ultramicrocellular filaments at two ends per inch (about 0.79 end percm.). The other warp and all of the fill yarns were of 2-ply, 3S-twisted, 180 denier, Dacron polyester yarn. Weaving was programmed toprovide a tightly woven Dacron fabric with 60 ends and 44 picks per inch(about 23.6 ends and 17.3 picks per cm.). Picks were inserted in such away that about every 0.125 inch (0.318 cm.) along each foamfilament ofthe first warp a pick went around the foamfilament to stitch it to theback face of the forming Dacron fabric. Area weight of the finishedfabric was 9.33 oz./yd. (0.317 kg./m.

The Dacron polyester yarn employed was a continuous-filament yarnprepared from polyethylene terephthalate homopolymer with a relativeviscosity of 30 (measured in a solvent composed of phenol and 2,4,6-trichlorophenol mixed 100/70 by weight). Drawn in a draw-bath about 6 C.hotter than usual and at a very low drawratio, the yarn produced had avery high elongation at break of 71% and a low shrinkage in boilingwater of 6.7%.

Three specimens about 1 foot square (about 0.3 meter square) were cutfrom the woven, two-layer fabric, and each was molded into a mediumbrassiere cup in a typical ring and plug mold. The fabric specimen wasclamped to the ring, and then the brassiere-cup-shaped, heated, maleplug was pushed down through the ring to mold a cup. Just before eachsample was clamped to the ring, it was immersed for several minutes in abath of methylene chloride and 1,1,2-trichloro-1,2,2-trifluoroethane(50:50 by volume at room temperature), thus causing thechlorofluorocarbon to permeate into the foam-cells. The heated male plugwas inserted for about 30 sec. in each case. At 150 C., the fabric wasbadly degraded. At 130 C., a good brassiere-cup formed with only a tinyarea of fabric degradation, but the foam-filaments did not fullyinflate. At C., an excellent cup was formed with no separation of picksin the fabric. Not only did the heated mold heat-set the molded fabricto a stable shape, but it also caused the foam-filaments to fullyinflate. In each case the foam-filament layer was against the heatedplug.

These results show that, by proper selection of molding conditions,deep-drawn molded objects are readily obtained using fabrics comprisingboth elongatable dense yarns and collapsed microcellular filaments.Post-inflation of the microcellular filaments in the fabric creates bulkand excellent pneumatic cushioning. This technique is particularlyuseful for forming molded, conformable, cushioning, and decorativeupholstery coverings.

What is claimed is:

1. A process for producing an inflated foam fabric which comprises:

providing gas-inflated microcellular foam filaments of a thermoplasticsynthetic organic polymer, substantially all of the polymer beingpresent as film-like walls of less than about 2 microns thickness, thewalls defining polyhedral shaped, closed, uniform-sized cells having amaximum transverse dimension less than about 1000 microns;

collapsing the filaments by reducing the quantity of gas within thecells;

forming the collapsed filaments into a fabric; and

reinflating the filaments by introducing a gas into the cells.

2. The process of claim 1 wherein said microcellular filaments areultramicrocellular filaments, said polymer being a crystalline polymerand exhibiting in the cell walls uniplanar orientation and uniformtexture.

3. The process of claim 2 wherein said polymer is selected from thegroup consisting of stereo-regular polypropylene and polyethyleneterephthalate.

4. The process of claim 1 wherein the fabric is a woven fabriccontaining said microcellular filaments in both warp and weft.

5. The process of claim 1 wherein said microcellular filaments have afully inflated diameter of from about 0.01 inch to about 0.25 inch.

References Cited UNITED STATES PATENTS 2,913,769 11/1959 Kastli 161-178X 3,100,926 8/1963 Richmond 28-75 3,227,664 1/1966 Blades et al. 2602.53,244,545 4/1966 Marzocchi et a1. 139-420 X 3,344,221 9/1967 Moody etal. 264321 LOUIS K. RIMRODT, Primary Examiner.

